Another noteworthy fact that can be derived from the optical spectrum is the remarkable width of the forbidden lines. All of them have FWHM of the order of 900 km s\(^{-1}\)  after correcting for instrumental resolution, which is significantly broader than what is typically seen in AGN [1]}. Assuming that, as hypothesized by [2]}, there is a correlation between the forbidden lines width and the stellar velocity dispersion \(\sigma _*\) , we can derive \(\sigma _* \sim \) 330 km s\(^{-1}\) , using its scaling relation with the FWHM([O II]) derived by [3]}. Such a value would be high even for a large elliptical galaxy [4]}, but the host galaxy of PKS 2004-447 is a spiral galaxy with pseudobulge [5]}. This suggests that, at least in our source, the forbidden lines width does not obviously correlate with the stellar velocity dispersion. A possible alternative origin for the observed large width may instead be interaction through shocks between the NLR gas and the relativistic jet. Shocks can indeed produce turbulent motion in the gas, which in turn causes the lines to become broader [6]}, [7]}, [8]}. The presence of jet/NLR interaction may also explain the rather high temperature we have derived in Sect. REF , which is above the typical value observed in AGN [9]}. Further investigation, especially by means of integral-field spectroscopy, can clarify this aspect.
